The present invention relates to a silicon article processed by a semiconductor technique, and more particularly, relates to a silicon article having columns which is particularly suited for use as a filter, especially a charge and particulate selective filter, or as a heat sink.
An advantage of processing techniques used in the semiconductor industry is that silicon structures can be made which have very fine submicron dimensions. Typically, such semiconductor processing techniques are used to make the wiring lines, trenches and other features of semiconductor devices. The present inventors, however, have invented new silicon structures which deviate from those found in present day semiconductor devices. Among these structures are those found particularly useful for filters, especially charge and particulate selective filters, and heat sinks.
The prior art is replete with various structures and apparatus for filter and heat sink applications. Prior art relating to filters will be discussed first.
Hoenig U.S. Pat. No. 3,475,882, the disclosure of which is incorporated by reference herein, discloses a chamber for separating gases based on their charge. The chamber further includes plates, coated with n-type and p-type semiconductor materials, on which a gas is adsorbed.
Thompson U.S. Pat. No. 5,332,485, the disclosure of which is incorporated by reference herein, discloses an electrostatic filter consisting of parallel electrodes separated by porous filter material. The porous filter material is meant to collect the fine particles only after they have been agglomerated.
Hattori et al. U.S. Pat. No. 5,466,279, the disclosure of which is incorporated by reference herein, discloses an electric dust collection system in which dust particles are first ionized and then collected on collector electrodes. A metal oxide semiconductor layer is formed on the collector electrodes. Particles are only separated by charge and then collected.
El-Shoubary et al. U.S. Pat. No. 5,480,558, the disclosure of which is incorporated by reference herein, discloses a crude apparatus for cleaning soils of contaminants. In one embodiment shown in FIG. 4, the apparatus consists of a platinum or carbon electrode embedded in a plurality of porous bags filled with an adsorbent material. The electrode attracts the contaminants which are adsorbed by the adsorbent material in the bag.
As is apparent from the above prior art, there is opportunity for improvement of filters, particularly those filters which are charge and particulate selective.
Accordingly, it is a purpose of the present invention to have am improved filter, especially an improved charge and particulate selective filter.
Turning now to prior art related to heat sinks, Weichold et al. U.S. Pat. No. 5,179,043, the disclosure of which is incorporated by reference herein, discloses micro heat pipes cut into semiconductor devices. The micro heat pipes are partially filled with heat conductive films to improve cooling.
Bernhardt U.S. Pat. No. 5,218,515, the disclosure of which is incorporated by reference herein, discloses a microchannel heat sink formed on the back side of a semiconductor device.
Azar et al. U.S. Pat. No. 5,304,846, the disclosure of which is incorporated by reference herein, discloses a semiconductor material heat sink having fins and channels. As shown in FIG. 16 of this reference, the heat sink is many times bigger than the semiconductor device that it is to cool.
Bertin et al. U.S. Pat. No. 5,506,753, the disclosure of which is incorporated by reference herein, discloses a semiconductor device having grooves on the inactive side for cooling. The grooves are 125-250 microns deep and 500-1000 microns wide.
In view of the above references, it would be desirable to have a heat sink that is improved in performance.
Accordingly, it is another purpose of the present invention to have an improved heat sink.
According to a first aspect of the invention, there is disclosed a silicon article comprising:
a silicon base portion; and
a plurality of columns extending from said base portion, said columns being circular or elliptical in crossection and comprising polysilicon or a metal, said columns defining open areas between said columns.
According to a second aspect of the invention, there is disclosed a method of making a silicon article comprising the steps of:
(a) applying a photoresist to a silicon substrate;
(b) exposing and developing said photoresist to form a pattern of openings;
(c) etching said silicon substrate through said pattern to form a pattern of trenches in said silicon substrate;
(d) removing said photoresist;
(e) heating said silicon substrate in a suitable atmosphere to form a thin oxide or nitride coating on the surface of said trenches;
(f) filling said trenches with polysilicon or a metal; and
(g) removing said silicon surrounding said trenches to thereby leave columns of polysilicon or metal surrounded by said oxide or nitride coating.